A 4-heteroaryl-N-(2-phenyl-[1,2,4]triazolo[1,5-a]pyridin-7-yl)-1H-pyrazole-5-carboxylic acid amide derivative represented by formula (I) exhibits excellent PDE10 inhibitory activity, is useful for treating and/or preventing a variety of symptoms of mental disorders linked to PDE10 (for example, paranoid type, disorganized type, catatonic type, undifferentiated and residual type schizophrenia, and the like), and has potential as a therapeutic agent having diminished adverse reactions.
As a method for manufacturing an N-([1,2,4]triazolo[1,5-a]pyridin-7-yl)-1H-pyrazole-5-carboxylic acid amide derivative (formula (i)), scheme 1 on page 26 of WO 2012/076430 (PTL 1) discloses a manufacturing method in which a carboxylic acid derivative (formula (ii)) and a 7-amino-[1,2,4]triazolo[1,5-a]pyridine derivative (formula (iii)) are subjected to a condensation reaction.

As a method for manufacturing a 4-heteroaryl-N-(2-phenyl-[1,2,4]triazolo[1,5-a]pyridin-7-yl)-1H-pyrazole-5-carboxylic acid amide derivative (formula (I-a)), page 184 of WO 2014/133046 (PTL 2) discloses a manufacturing method in which a carboxylic acid derivative (formula (CA)) and a 7-amino-[1,2,4]triazolo[1,5-a]pyridine derivative (formula (AM)) are subjected to a condensation reaction.

According to PTL 1, a compound represented by formula (iii) is manufactured using 0-(mesitylsulfonyl)hydroxylamine (formula (v)).

A compound represented by formula (I) in the present invention can be manufactured using a compound represented by formula (iii) disclosed in PTL 1, but in cases where a compound represented by formula (iii) is manufactured according to the manufacturing method disclosed in PTL 1, it is essential to use the compound represented by formula (v). However, it has been pointed out that the compound represented by formula (v) is not suitable for use in large scale synthesis or industrial manufacturing due to problems relating to the stability and safety of the compound (see NPL 1). Therefore, in cases where large scale synthesis or industrial manufacturing of a compound represented by formula (I) is being considered, it is essential to find a novel manufacturing method that is different from the manufacturing method disclosed in PTL 1.
Meanwhile, a method for manufacturing an analogous compound to formula (iii) (formula (iii-1)) is disclosed in WO 2013/117610 (PTL 3). However, the yield of a compound having a RV═NH2 group is low, at 28%, and there are no synthesis examples of 6,7-2 substituted [1,2,4]triazolo[1,5-a]pyridine derivatives.

In addition, no manufacturing method is known whereby a 6-fluoro-7-amino-4-phenyl-[1,2,4]triazolo[1,5-a]pyridine derivative, which is a partial structure of a 4-heteroaryl-N-(2-phenyl-[1,2,4]triazolo[1,5-a]pyridin-7-yl)-1H-pyrazole-5-carboxylic acid amide derivative represented by formula (I), can be synthesized in large quantities with good efficiency.
Therefore, there is a need to overcome these problems and establish an efficient manufacturing method that is suitable for large scale synthesis or industrial manufacturing of a compound represented by formula (I).